Quote Originally Posted by Rudeofus View Post
I've been looking for information on that for a while and came up empty. Fact is that the Selenium in selenium toner is so toxic that few home brewers are willing to mix this toner from raw chemicals - at least I definitely wouldn't. Therefore I don't think we will see much published data on that.

Among the later books on photo chemistry are Haist's two volumes, and these books don't even mention Ammonium Thiosulfate. Why? Because Kodak would have stomped on Haist's feet if he would published trade secrets! What does this tell me? There isn't much published about modern fixers, at least not with solid data and reproducible results, and even patents are mostly vague or intentionally misleading. Most published data (formulas and test results, not instruction manuals) on fixers is simply not applicable to modern products.

Testing, at least at amateur level, is much easier for fixers than for developers. Measuring speed and grain (as Mark Overton did) requires some apparatus, and measuring sharpness (reliably!) is beyond reach for most of us. Measuring clearing speed is trivial, and tests for residual silver and hypo are cheap and available, with published recipes. The biggest obstacles to fixer improvements at the amateur level are the cheap availability of commercial rapid fixer (most of the time these commercial soups cost half or less of what the raw chems would cost us!) and the fact that fixers don't visibly improve your prints (for the first 10 years at least).

Is there a motivation for home brewing or testing fixers? Apparently TF-5 fixer runs circles around standard commercial rapid fixers, especially in terms of working solution life, but it's economically unfeasible to ship it across continents and its recipe is unpublished. A version of Farmer's reducer would be nice that has a working solution life of 8 hours (one really long dark room session). Likewise there is little to no data available for alkaline fixers, or even just simple data points like "what's the most economical way of archival fixing for TMX/TMY that leaves no magenta stain?" or "how can I translate a fixer's clearing time of film X into archival fixing time of paper Y?".
Haist does talk about Ammonium Thiosulfate, and includes several formulas. I would say it isn't really modern and/or rapid fixers that aren't discussed in publications, rather modern alkaline and/or non hardening rapid fixers that aren't discussed. The fixers in Haist, whether Sodium or Ammonium based, are mostly hardening fixers, which normally require acidity.